To be a solipsist is to be unresponsive to others' reasons, intentions, desires, experiences and so on.
Let the sum of "reasons, intentions, desires, experiences, and so on" be referred to by the term 'subjectivity'. Subjectivity does not refer to the person who has these things, but is what such a person has.
What I mean when I say that someone is responsive to something is that it matters to them that it exists, they take it into account as they plan their way of living, or have reasons why they need not do so.
To communicate is to provide for another one's own subjectivity.
There are two options one has when another attempts to communicate with one. Either to be responsive or not.
One way to respond to someone's subjectivity is to hold that there is a problem with it. One way to be unresponsive to someone's subjectivity is to not care how it is one way or another.
For me to hold that my subjectivity is fine, whatever you or anyone says, is to hold that my subjectivity may not properly be responded to in any way which puts it into question. I therefore am forced to hold that it is improper for you to question my intentions and desire, etc., unless you are merely seeking information. What you may not do in this case is question because you find my position untenable for some reason, whether that be morally or logically.
When this is done, I effectively request that others treat me as nothing. That is, I request that others treat me as a solipsist would. Now, I may hold that I may yet put your views into question, but this would also be a kind of solipsism, as I would be unwilling to address as possibly legitimate the actual roots of your position, since I already know that I am right.
Now, to be intersubjective is the opposite of being solipsistic. It is to respond to others' subjectivities as important, and to recognize the potential error in each of our subjectivities, and to be willing to learn from one another. It is to allow one's own subjectivity to be in question at a certain level.
This does not mean withholding any degree of certainty about whether you are right about anything. We each hold certain things more or less strongly. The issue is to be willing to give an account as to why one holds one's views about things, that is, to be willing to answer questions.